Infections caused by Candida albicans and other related fungal species continue to have a sustained prevalence worldwide (Nyirijesy American Family Physician (2001) 63:697-702). The wide spectrum of candidiasis and its recognized clinical importance has stimulated interest in understanding the various fungal and host components involved in the pathogenesis of these diseases. C. albicans is a human commensal and its interaction with the host immune system plays an important role both in the commensalism and in controlling the infection. Several potential antigenic targets of the host response against C. albicans have been investigated with the ultimate aim to generate immunological tools to fight candidiasis. The most investigated antigenic targets include mannoproteins (MP), some with adhesive or receptor-like functions, heat shock proteins, enolase and secretory aspartyl proteinases (Sap) (Schaller et. al., J. of Invet. Dermatology (2000) 114: 712-717). Together with recent advances in the mechanisms of anti-candidal immune responses, these studies have laid the groundwork for further investigations into the selected use of some of the above targets as potential therapeutic or preventive vaccines or for producing antibodies for passive vaccination.
It has previously been found that expression of a member of the Sap family of C. albicans, Sap2, is critically required for infection, and that intravaginal or even intranasal immunization with full-length wild type Sap2 conferred an elevated degree of protection against Candida infection (de Bernardis, Infect and Imm. (2002) 70, 2725-2729). However, wild type Sap2 protein was shown to be enzymatically active, very unstable, and endowed with toxicity potential (Schaller et al, Infect and Imm (2003), 71, 3227-3234) making it a poor choice for a vaccine.
Therefore, there is a need in the art for a Sap2 antigen that is capable of eliciting efficient antibody and cellular immune responses against C. albicans without having the drawbacks of the full-length wild type Sap2 associated thereto.